Volek and Phinney- the art and science of low carbohydrate living
They also have videos posted on you tube -
150g protein per day for the first three weeks to preserve lean muscle mass then macros to suit your body (ketogains.com has a calculator).
Measure macros in grams
Carb is a limit, protein a goal and fat is a lever (again you don’t have to eat the whole macro per day and your body will make up the difference by burning it’s own fat stores for fuel)
Track everything that way you know what to adjust when required